Generalise build --ghc-option flag to --prog-option for any prog

and remove makefile --ghc-option flag as it's not used (as far as I can see).
It works generically by updating the ProgramConfiguration rather than the
previous ad-hoc implementation. This feature is generally only useful for
hackers who want to pass extra args to a progam during the build step
(probably as a one-off) without having to reconfigure.